Galvanic corrosion

When different metals are used together, and there is direct contact between them, we must consider a specific type of corrosion, namely galvanic corrosion. Examples: aluminum sheets anchored with stainless steel fasteners, use of copper and metal, ...

The combination of some metals causes few problems, while the combination of other metals in a risky situation (e.g., as part of a load-bearing structure) can cause serious problems.

Two materials such as stainless steel and aluminum, both considered corrosion-resistant, are best not combined. Preferably, the same materials should be combined in a workpiece, as well as fasteners of the same material.

What exactly happens with galvanic corrosion? A potential difference between the two metals causes the weaker metal to corrode. And, of course, certain environmental conditions or substances can only accelerate this effect. Preferably, the same materials are always used together; if this is not possible, there are two options: either ensure that the two metals do not come into direct contact by working with a plastic insulator, or look up in tables which materials can be combined and which cannot.

There are two commonly used types of tables. The first table can be found via this link to the English Wikipedia, where potential differences determine whether materials can be combined. A second type of table works with codes (A to E), where the combination A causes no problems, and the combination E is completely discouraged, with several intermediate variations. This table can be downloaded at the bottom of this page.